Sinkhole risk in Union County, OH: Pockets of it

Pockets of it

Soluble rock at the surface or under thin cover in part of the county.

On soluble rock: 100%
At or near the surface: 0%
Buried under cover: 100%

The next step for one property

Check the parcel against your state survey sinkhole map, and ask for an inspection if cracks, depressions or sticking doors show up.

That works out to roughly 432 of Union County's 432 square miles on soluble rock. With about 71,721 residents (166 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 315 map points about 1.2 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Union County

The nearest county rated sinkhole country is Monroe County, MI, about 112 miles north. 1 of the 6 closest counties land in the same band; the ground changes quickly around here.

Delaware County, OH 19 mi east · 0% at surface
Logan County, OH 22 mi west · 0% at surface
Marion County, OH 23 mi northeast · 0% at surface
Champaign County, OH 24 mi southwest · 0% at surface
Madison County, OH 28 mi south · 0% at surface
Franklin County, OH 29 mi southeast · 0% at surface

Which formation it is

The largest mapped soluble unit here is the Salina Group (dolostone (dolomite)), Silurian in age, covering about 70% of the county. Next is the Tymochtee and Greenfield Formations, Undivided at 24%.

Against the rest of Ohio

Union County ranks 80 of 88 in Ohio for soluble rock at the surface, and sits above 0% of US counties on that measure.